1. Field of the Invention
The invention relates to a method for improving the mechanical properties of a glass-fiber mat obtained by applying a binder containing an aqueous phenolic condensation resin to the mat and hardening the binder.
2. Discussion of the Related Technology
Glass-fiber mats are used mainly as thermal insulating material. The binder is supposed to bind the fibers firmly together to obtain a coherent structure. The binder is at the same time supposed to ensure sufficient elasticity of the insulating material and high recovery thereof after compression so that the insulating material can be stored, transported and deformed for use at the final location.
U.S. Pat. No. 4,663,419 discloses using for a glass-fiber mat a binder containing a condensation product from phenol, formaldehyde and urea condensed in the presence of a basic catalyst, and additional urea and further additives, namely silane, mineral oil, ammonia and ammonium sulfate. The binder is sprayed as an aqueous solution on the raw mat that is then pressed and put in the desired form for the insulating material, for example a panel or a pipe, after which it is fed to a curing oven where the binder is hardened.
U.S. Pat No. 4,176,105 discloses a binder for a glass-fiber mat which is obtained by reaction of a phenol-formaldehyde-urea condensation resin with boric acid and urea. Per 100 parts by weight of phenol-formaldehyde-urea condensation resin 12 to 16 parts by weight of boric acid are added. When the resin hardens a boric acid complex is formed. This is intended to increase the resistance of the binder to punking at high temperatures.
However, known binders leave something to be desired with respect to the mechanical strength of the glass-fiber mat, in particular the tensile strength and the recovery after compression of the mat, especially after it has been stored for some time.